1. Field of the Invention
The present invention relates to a sheet handling unit for placing sheets outputted from an image processing apparatus such as a printer, an electrostatographic copying machine or a facsimile machine in a designated mail tray or a predetermined tray.
2. Description of Related Art
Image processing apparatuses such as printers are often shared by plural information processors such as computers and workstations via networks. In such a case, a single printer, for example, is shared by plural users. The term "user" herein means a single person or a group of persons.
Such a so-called network printer is preferably equipped with a sheet handling unit called a "mailbox unit" which is adapted to place sheets outputted on the basis of each user's print information into the corresponding user-specific mail tray.
With an increase in the processing speed of the image processing apparatuses, there occurs a demand for a sheet handling unit capable of stacking a large volume of sheets. Further, it is often desired that the sheet handling unit additionally has post-processing functions such as a stapling function.
FIG. 15 shows one exemplary sheet handling unit of the prior art which satisfies the aforesaid demands. The sheet handling unit 41 is used in connection with a printer 42, and includes a sheet introduction path 43 for introducing a sheet outputted from the printer 42. The introduction path 43 is branched into an upper and lower branch paths 43a, 43b. The upper branch path 43a guides the sheet to a processing station 45 having a stapling mechanism 44 for stapling a stack of plural sheets. The lower branch path 43b is connected to a sheet transportation mechanism 47. The sheet transportation mechanism 47 discharges a sheet selectively to any one of plural mail trays 48 arranged in a vertically spaced and tiered relation adjacent a lower portion of a unit body 52.
A stacker 46 for receiving a large volume of sheets delivered from the processing station 45 is provided in a vertically movable manner above the plural mail trays 48. Provided in the unit body 52 is a sheet delivering mechanism 49 for delivering a sheet to a designated one of the mail trays 48 or to the stacker 46 on the basis of sheet destination information applied thereto from an information processor.
The sheet delivering mechanism 49 includes a first path switching claw 50 for delivering a sheet switchably to the sheet transportation mechanism 47 or to the stacker 46 on the basis of the sheet destination information, and second path switching claws 51 for delivering the sheet transported thereto via the sheet transportation mechanism 47 switchably to any one of the mail trays 48 on the basis of the sheet destination information. With this arrangement, the sheet handling unit can stack sheets (which may be stapled as required) on the stacker 46, and place sheets respectively carrying images recorded thereon on the basis of print information outputted from different information processors in the respective mail trays 48 for assortment thereof.
With the sheet handling unit of this arrangement, however, plural sheets to be discharged onto the mail tray 48 cannot be subjected to the stapling process.
To overcome this problem, the inventors of the present invention have developed a sheet handling unit 62 as shown in FIG. 14.
This improved sheet handling unit 62 includes a processing station 64 having a sheet stapling mechanism 63 and provided in a vertically movable manner in a unit body 65. A plurality of mail trays 66 are fixed to an upper portion of the unit body 65 in a vertically spaced and tiered relation. A vertically movable stacker 61 is provided below the mail trays 66. Further provided in the unit body 65 are an elevating mechanism for moving up and down the entire processing station 64 and a control unit (not shown) for controlling the elevating mechanism. Sheets are stapled as required, and then discharged to any designated one of the mail trays 66 or to the stacker 61 by moving up or down the processing station 64.
With this arrangement, the sheet handling unit can stack a large volume of optionally stapled sheets on the stacker 61, and discharge stapled sheets in any designated one of the user-specific mail trays 66.
Unfortunately, the improved sheet handling unit 62, which is arranged to move up and down the heavy processing station 64 with the sheet stapling mechanism 63, has a complicated and bulky structure and requires a high-power drive source. Therefore, the unit suffers from significant increase in size and costs.
The sheet handling unit 62 has another drawback that the provision of a sheet sorting mechanism is difficult. More specifically, where plural copies of a single plural-page document are sequentially printed, it is preferred that plural stacks of print-out sheets are discharged discretely on a copy-by-copy basis in a mail tray or stacker. Further, where plural documents are sequentially printed, it is preferred that plural stacks of print-out sheets are discharged discretely on a document-by-document basis in a mail tray or stacker.
A so-called offset sheet discharging mechanism is known as a mechanism serving for this purpose. The offset sheet discharging mechanism is adapted to discharge respective sheet stacks in slightly different discharge positions in a tray for assortment. Addition of such an offset discharging mechanism to the aforesaid sheet handling unit 62 requires a mechanism for shifting the entire processing station 64 in a sheet widthwise direction. This results in an even more complicated construction of the unit and a significant increase in costs.